Platinum-styrene complexes which promote hydrosilation reactions

ABSTRACT

Platinum-styrene complexes are prepared by reacting a platinum halide with styrene or substituted styrenes in the presence of a basic material for a sufficient amount of time to form a complex having more than one and less than four gram atoms of halogen per gram atom of platinum. 
     These platinum-styrene complexes may be used to promote the addition of organosilicon compounds having at least one .tbd.SiH group per molecule to a compound containing aliphatic unsaturation.

This is a division of application Ser. No. 230,462, filed Feb. 2, 1981,now U.S. Pat. No. 4,394,317.

The present invention relates to platinum complexes and moreparticularly to platinum-styrene complexes having improved stabilitywhich promote hydrosilation reactions.

BACKGROUND OF THE INVENTION

Various platinum compounds and complexes have been used heretofore topromote hydrosilation reactions. The platinum compounds and complexeswhich have been used to promote hydrosilation reactions such as theaddition of organosilicon compounds containing .tbd.SiH groups tocompounds containing aliphatic unsaturation are compounds such aschloroplatinic acid, platinum chloride-olefin complexes, platinumchloride-cyclopropane and complexes derived from the reaction ofalcohols, ethers, aldehydes, ketones and vinyl siloxanes withchloroplatinic acid.

While chloroplatinic acid and elemental platinum may be used ascatalysts for hydrosilation reactions, they have certain disadvantages.For example, chloroplatinic acid is insoluble in many organic solventsand is not always effective at low concentrations. Moreover, thesecatalysts are subject to poisoning in the presence of a number of commonmaterials. The disadvantages of elemental platinum and chloroplatinicacid with respect to poisoning and speed of reaction have been overcomeby the use of the platinum compounds described above, such as theplatinum-olefin complexes described in U.S. Pat. Nos. 3,159,601 and3,159,662 to Ashby. Faster and more active catalysts are described inU.S. Pat. Nos. 3,715,334; 3,775,452; and 3,814,730 to Karstedt, in whichplatinum vinyl siloxane complexes are treated with a base material toform a catalyst in which the halogen to platinum ratio is about 1:1 orless than 1:1.

It has been found that a platinum-styrene complex which is formed in thepresence of a basic material and has a halogen to platinum ratio of morethan one, but less than four gram atoms of halogen per gram atom ofplatinum, is substantially more stable than other platinum complexes andmaintains its level of activity for longer periods of time.

Therefore, it is an object of this invention to provide a novel platinumcatalyst. Another object of this invention is to provide a platinumcatalysts for effecting the addition of SiH-containing organosiliconcompounds to unsaturated organic compounds. Still another object of thisinvention is to provide a catalyst which is highly reactive at roomtemperature and is more effective at lower concentrations. A furtherobject of this invention is to provide a catalyst which is more stableand maintains its level of activity for longer periods of time.

SUMMARY OF THE INVENTION

The foregoing objects and others which will become apparent from thefollowing description are accomplished in accordance with thisinvention, generally speaking, by providing a process for preparing aplatinum complex which comprises reacting a platinum halide with styreneor substituted styrenes in the presence of a basic material to form aplatinum complex which contains more than one and less than four gramatoms of halogen per gram atom of platinum. The resultant complex may beused to promote the addition of organosilicon compounds containingsilicon-bonded hydrogen to unsaturated organic compounds.

DETAILED DESCRIPTION OF THE INVENTION

Platinum complexes are known in the art and their preparation andproperties are described, for example, in "Coordination Compounds ofOlefins with Metallic Salts," R. N. Keller, Chemical Reviews, 1940-41,27-28, pages 229-267; and Joy and Orchin, Journal of the AmericanChemical Society, 81, pages 305-311 (1959). The olefin portion of theplatinum complexes of this invention is styrene and ring substitutedstyrenes. Examples of substituted styrenes are alkyl ring substitutedstyrenes such as m-methylstyrene, p-ethylstyrene, p-ethoxystyrene andthe like. The platinum complexes of this invention are prepared byreacting a platinum halide with styrene or substituted styrenes in thepresence of a basic material. Examples of suitable basic materials arealkali metal carbonates, such as sodium carbonate, potassium carbonateand sodium bicarbonate.

Although, the amount of base employed is not critical, a sufficientamount of base should be present to neutralize at least some of theavailable halogen. Even though less than a stoichiometric amount can beemployed, it is preferred that a stoichiometric amount or even a slightexcess be employed in order to neutralize enough of the availablehalogen to form a complex containing more than one and less than fourgram atoms of halogen per gram atom of platinum.

The platinum-styrene complex of this invention is prepared by reacting aplatinum halide, such as chloroplatinic acid, with styrene in thepresence of a base and preferably an alcohol at a temperature of from 0°to 130° C., preferably at a temperature from 25° to 100° C. and morepreferably at a temperature of from 40° to 60° C. Also, it is possibleto form a platinum-styrene complex in the absence of the base andthereafter react the platinum complex with the basic material tosubstantially reduce the halogen content of the resultant catalyst.

The reaction between the platinum halide, styrene and base is dependenton the amount of base present and the temperature. Thus, the reactiontime varies inversely with the temperature, i.e., the higher thetemperature, the shorter the reaction time and conversely, the lower thetemperature, the longer the reaction time. When the reaction temperatureis in the preferred range, i.e., from 40° to 60° C., the reaction timevaries from about one hour to about 0.25 hours.

The reaction may be conducted at atmospheric pressure or below or aboveatmospheric pressure. Preferably, the reaction is conducted atatmospheric pressure.

The platinum halide such as chloroplatinic acid which is employed in thereaction with the olefin is commercially available in the form ofchloroplatinic acid hexahydrate,

    H.sub.2 PtCl.sub.6.6H.sub.2 O,

however, the material can be used in the anhydrous form or it can beused as the hexahydrate.

Suitable solvents which may be employed in the preparation of theplatinum-styrene complexes of this invention are alcohols having from 1to 6 carbon atoms such as methanol, ethanol, propanol, butanol andhexanol and aromatic hydrocarbon solvents such as benzene, toluene andxylene. It is preferred that the solvent be an alcohol and morepreferably ethanol. Mixtures of alcohols or alcohols and aromatichydrocarbons may be used. The amount of solvent is not critical and mayrange from about 1 to 100 parts and more preferably from about 10 to 50parts per part of platinum halide.

The platinum-styrene complexes of this invention are effective for theaddition of organosilicon compounds containing silicon-bonded hydrogento organic compounds having carbon-carbon unsaturation. The catalysts ofthis invention are effective for the addition reactions described inU.S. Pat. Nos. 2,823,218 to Speir et al, 2,970,150 to Bailey and3,220,970 to Lamoreaux.

Suitable monomeric silicon compounds and organosilicon compoundscontaining silicon-bonded hydrogen which may be used in the presentinvention are those represented by the formula ##STR1## in which R is analkyl, cycloalkyl, alkaryl, aralkyl, haloalkyl or haloaryl radicals, Xis a hydrolyzable radical, such as halogen, alkoxy radicals, aryloxyradicals and acyloxy (OOCR) radicals; c is a number of from 0 to 3, d isa number of from 1 to 3; and the sum of c and d is from 1 to 4. Whenmore than one R radical is present in the compound the various Rradicals may be the same or different.

Among the radicals represented by R are alkyl radicals, e.g., methyl,ethyl, propyl, octyl and octadecyl radicals; cycloalkyl radicals such asthe cyclohexyl and cycloheptyl radicals; aryl radicals such as thephenyl, biphenyl, alkaryl radicals such as tolyl and xylyl radicals;aralkyl radicals such as the benzyl and phenylethyl radicals; haloarylradicals and haloalkyl radicals such as the chlorophenyl, chloromethyland the dibromophenyl radicals. Preferably, R is a methyl or a mixtureof methyl and phenyl radicals.

Examples of suitable silicon compounds represented by the above formulawhich can be employed in the present invention are:methyldichlorosilane, phenyldichlorosilane, diethylchlorosilane,dimethylethoxysilane, diphenylchlorosilane, dichlorosilane,dibromosilane, pentachlorodisiloxane, and the like.

Suitable silicon-bonded hydrogen containing which may may be used in thepresent invention are those in which each molecule contains at least onesilicon-bonded hydrogen. Suitable examples of such compounds areorganopolysiloxanes and various polysilalkylene compounds containing,for example, an --Si--Y--Si-- linkage in which Y is a divalenthydrocarbon radical having from 1 to 8 carbon atoms or a nitrogen atom,such as organosilazanes, having the --Si--N--SI-- linkage in thepolymer.

Suitable examples of organopolysiloxanes are polymers and copolymerscontaining up to one or more of the units having the formulae: R₃SiO₀.5, R₂ SiO, RSiO₁.5 or SiO₂ along with at least one unit permolecule having the formulae: RHSiO, R₂ HSiO₀.5, HSiO₁.5, H₂ SiO, RH₂SiO₀.5 wherein R is the same as above. Any of the silicon hydrogencompounds described above, are operative in the practice of the presentinvention, however, it is preferred that the silicon hydrogen compoundbe an organopolysiloxane such as an organopolysiloxane (RHSiO)_(n) or anorganopolysiloxane polymer or copolymer having the formula R_(y) SiH_(z)O_(4-y-z) where R is the same as above, n is a number of from 1 to20,000, y is a number of from about 0.5 to 2.49 and z is a number offrom 0.001 to 1 and the sum of y and z is a number equal to from 1 to2.5.

Compounds contaning carbon-to-carbon unsaturation, particularlyunsaturated compounds containing olefinic or acetylenic unsaturationwhich can react with the organic compounds described above containingthe silicon-bonded hydrogen are monomeric and polymeric compoundscontaining aliphatic unsaturation. These compounds can contain onlycarbon and hydrogen or they may also contain another element orelements. Where the aliphatically unsaturated compounds contain anelement other than carbon and hydrogen, it is preferred that the otherelement be oxygen, halogen, nitrogen, silicon or mixtures thereof.Aliphatically unsaturated compounds which may be employed that have asingle pair of carbon atoms linked by multiple bonds are for example,ethylene, propylene, butylene, octylene, styrene, butadiene, pentadiene,2-pentene, 2-divinylbenzene, vinyl acetylene and the like. Preferablythe unsaturated compound does not contain more than about 24 carbonatoms in the chain.

Included in the oxygen containing unsaturated compounds which may beemployed in the practice of the invention are methylvinylether,divinylether and the like; the monoalkylethers of ethylene glycol, allylaldehyde, methylvinyl ketone, phenylvinyl ketone, acrylic acid,methylmethacrylate, phenylmethacrylate, vinylacetic acid, vinyl octoate,vinyl acetate, maleic acid, linoleic acid and the like. Otherunsaturated compounds which may be employed are cyclic and heterocyclicmaterials containing aliphatic unsaturation in the ring, such as,cyclohexene, cycloheptene, cyclopentadiene, dihydrofuran, dihydropyreneand the like. The sulfur analogues of the unsaturated oxygen containingmaterials may also be employed in the practice of this invention. Inaddition to compounds containing carbon, hydrogen, oxygen and sulfur,compounds containing other elements may also be employed. Thus,halogenated derivatives of any of the materials described above can beemployed including the acyl chlorides as well as compounds containing ahalogen substituent on a carbon atom. Thus, halogen containing materialsinclude, for example, vinyl chloride, the vinyl chlorophenyl esters, theallyl esters of trichloroacetic acid and the like.

Other types of unsaturated materials which are useful in the practice ofthis invention include compounds containing nitrogen substituents suchas acrylonitrile, allylcyanide, nitroethylene and the like. Unsaturatedpolymeric materials containing aliphatic unsaturation such as polyesterresins prepared from polybasic saturated or unsaturated acids andpolyhydric unsaturated alcohols may also be used in the practice of thisinvention.

Other unsaturated compounds which may be used in the practice of thisinvention are those compounds containing silicon such as the materialcommonly referred to as organo-silicon monomers or polymers. The scopeof the organosilicon compounds which are applicable to the process isidentical to the scope of the silicon-bonded hydrogen compounds usefulin the practice of this invention. For example, the unsaturatedorganosilicon compounds are identical to the silicon-bonded hydrogencompounds, except that the silicon-bonded hydrogen is replaced bysilicon-bonded organic radicals containing at least one pair ofaliphatic carbon atoms having aliphatic unsaturation. Although it ispreferred that the organosilicon compounds be free of silicon-bondedhydrogen atoms, organosilicon compounds containing both silicon-bondedhydrogen atoms and silicon-bonded unsaturated radicals may be used. Theonly requirement of these unsaturated silicon compounds is that there beat least one unsaturated organic radical attached to a silicon atom permolecule. Thus, the unsaturated organosilicon compounds include silanes,siloxanes, silazanes, as well as monomeric or polymeric materials havingsilicon atoms joined together by methylene or polymethylene groups or byphenylene groups.

Examples of suitable unsaturated silicon compounds which may be used aremethylvinyldichlorosilane, vinyltrichlorosilane, allyltrichlorosilane,methylphenylvinylchlorosilane, phenylvinyldichlorosilane,diallyldichlorosilane, vinylcyanoethyldichlorosilane, cyclicpolysiloxanes such as the cyclic trimer of methylvinylsiloxane, cyclictetramer of methylvinylsiloxane, cyclic pentamer or methylvinylsiloxane,cyclic tetramer of vinylphenylsiloxane, linear or branched vinylterminated diemthylpolysiloxanes, trimethylsiloxy terminatedvinylmethylpolysiloxanes, ethylphenylpolysiloxanes and copolymersthereof.

The ratio of the silicon-bonded hydrogen compound and the unsaturatedcompound employed can vary over a wide range. Generally, onesilicon-bonded hydrogen is equivalent to one olefinic double bond orone-half acetylenic triple bond so that this equivalency establishes thegeneral order of magnitude of the two reactants employed. However, formany purposes it may be desirable to employ an excess of one of thereactants to facilitate the completion of the reaction or to insure thatthe reaction contains one or more pairs of carbon atoms linked bymultiple bonds. In general, however, the ratio of the reactants isselected so that there are present from about 0.5 to 20 silicon-bondedhydrogen linkages available for each unsaturated carbon-carbon doublebond and from about 1.0 to 15 silicon-bonded hydrogen linkages for eachcarbon-carbon triple bond.

To effect the addition reactions of the organosilicon compositions inthe presence of the platinum-styrene complexes of this invention, thereactants and catalyst are thoroughly mixed an allowed to react attemperatures of from 10° to 200° C. The time required for the additionreaction is a function of temperature. At a temperature of from about15° to 175° C. and more preferably from 20° to 150° C., the reactiontimes can vary from a few seconds up to about 10 minutes or moredepending upon the amount of catalyst complex employed.

In some cases, it is desirable to employ a solvent for one or bothreactants. The amount of solvent employed is not critical and can varyover a wide range. Obviously, the same material may in some cases serveboth as the reactant and as the solvent.

The amount of catalyst employed can vary over a wide range. It ispreferred that enough catalyst be employed to provide from about 0.5 to500 ppm by weight and more preferably from 2 to 500 ppm by weightcalculated as platinum and based on the weight of the total composition,including silicon compounds, platinum catalyst and any additionalmaterials.

One of the advantages of the novel catalysts of this invention is that avery small amount of the catalyst will effect the desired reactionbetween the silicon-bonded hydrogen compound and the unsaturated organiccompound. In addition, it has been found that the catalyst retains itslevel of activity even after storing for prolonged periods of time atelevated temperatures. Furthermore, the activity of the catalyst is suchthat silicon-bonded hydrogen containing organopolysiloxanes and vinylcontaining organopolysiloxanes can be cured very rapidly and thereforeused as potting or encapsulating compositions for electrical componentson assembly lines.

These organopolysiloxane compositions may contain in addition to thesilicon-bonded hydrogen containing organopolysiloxanes, and vinylcontaining organopolysiloxanes, other additives such as fillers, i.e.,silica, hydrogels, aerogels; treated fillers such as silicas which havebeen treated with, for example trimethylchlorosilane orhexamethyldisilozane to impart hydrophobic properties thereto, quartz,alumina, glass fibers, diatomaceous earth, organosilicon plasticizers,Ultraviolet stabilizers, heat stabilizers and the like. Other additiveswhich may be included in the compositions are those which retard orinhibit the addition of Si-bonded hydrogen to an aliphatic multiple bondat room temperature. Examples of such additives are benzotriazole,1,3-divinyl-1, 1,,3,3-tetramethyldisiloxane and/or2-methyl-3-butyn-2-ol.

The catalysts of this invention are combined with .tbd.SiH containingcompounds and organic compounds containing olefinic unsaturation to formelastomeric compositions. These compositions may be used as pottingcompounds, sealants, coatings and particularly as dental impressionmaterials.

When the compositions of this invention are to be stored for a period oftime prior to use, it is preferred that the catalyst be mixed with aportion of the organosilicon compound containing olefinic unsaturationand stored in one package. The remainder of the organosilicon compoundcontaining olefinic unsaturation is preferably mixed with theorganosilicon compound containing silicon-bonded hydrogen and stored asa second package. The two packages can then be mixed together at theappropriate time of their use and molded. If other materials are to beadded to the composition, they should be incorporated in the individualpackages during their preparation rather than adding those materialsduring the final mixing of the whole composition.

In preparing dental impression compositions, it is preferred that theorganosilicon compound containing olefinic unsaturation be adiorganopolysiloxane containing terminal triorganosiloxy groups in whichat least one vinyl group is present in each of the triorganosiloxygroups be mixed at room temperature with an organopolysiloxanecontaining at least three silicon-bonded hydrogen atoms per molecule andthe platinum-styrene complex of this invention. Other materials whichmay be added are additives such as the fillers described above,pigments, flavoring substances and plasticizers. The dental impressioncompositions of this invention can be used in accordance with theconventional methods of working when using dental impressioncompositions and employing the devices customarily used for suchpurposes.

Various embodiments of the invention are illustrated in the followingexamples in which all parts are by weight unless otherwise specified.

PREPARATION OF PLATINUM-STYRENE COMPLEX Example 1

A platinum-styrene complex is prepared by adding 6 parts of sodiumbicarbonate to a mixture containing 3 parts of chloroplatinic acid (H₂PtCl₆.6H₂ O), 6 parts of styrene and 50 parts of ethanol. The mixture isheated to reflux temperature, (about 55° C.) and refluxed for about 35minutes with agitation, and then cooled to room temperature. Theresultant mixture which contains orange crystals is filtered and thecrystals washed with about 30 parts of acetone. About 30 parts of xyleneare added to the filtrate which results in the formation of crystals.This mixture is filtered and the orange crystals are recovered anddried. Analysis of these crystals indicates that a platinum-styrenecomplex is formed having a platinum to chloride ratio of 1:3.1.

EXAMPLE 2

The procedure of Example 1 is repeated except that the mixture is heatedat60° C. for 38 minutes. The resultant product has a platinum tochloride ratio of 1:1.9.

Comparison Example 3

The procedure of Example 1 is repeated except that the mixture is heatedat70° C. for 55 minutes. The resultant product has a platinum tochloride ratio of 1:0.9.

Comparison Example 4

The procedure of Example 1 is repeated except that 6 parts of 1-dodeceneare substituted for the styrene.

A catalyst is obtained having a platinum to chloride ratio of 1:2.8.

Comparison Example 5

The procedure of Example 1 is repeated except that the sodiumbicarbonate is omitted. The resultant catalyst contains a platinum tochloride ratio of 1:4.0.

PREPARATION OF CROSSLINKED COMPOSITION

Example 6

(a) A mixture is prepared by adding 3 parts of fumed silica and 100parts of quartz powder to 7 parts of a methylhydrogenpolysiloxane havinga viscosity of 50 cs. at 25° C. and 100 parts of vinyl terminateddimethylpolysiloxane having a viscosity of 500 cs. at 25° C.

(b) The platinum-styrene complexes prepared in the above examples areeach dissolved in isopropanol to form a solution containing 0.75 percentby weight of elemental platinum. About 1.6 parts of the platinum-styrenecomplex solutions are added to 100 parts of vinyl terminateddimethylpolysiloxane having a viscosity of 500 cs. at 25° C. Theisopropanol is removed at reduced pressure and then 100 parts of quartzpowder and 3 parts of fumed silica are added to the vinyl terminateddimethylpolysiloxane catalyzed mixture. The resultant mixture containingabout 60 ppm of platinum, calculated as elemental platinum, is storedfor three days at room temperature.

A portion of each mixture is heated at 60° C. for various periodsoftime, cooled to room temperature and then combined with composition(a) above in equal parts and the time required for crosslinking "workingtime"is observed. A portion of each mixture is also stored at roomtemperature and combined with equal parts of (a) above. The stability ofthe catalyst is illustrated in the following table by changes in the"working times".

                  TABLE                                                           ______________________________________                                        Heat Aging Stability Data                                                               Heat Aging                                                          Example                                                                              Ratio    Time     Temperature                                                                             Working Time                               No.    Pt:Cl    (Hrs.)   (° C.)                                                                           (Seconds)                                  ______________________________________                                        1      1:3.1    24       60°                                                                              50                                                         72       25°                                                                              50                                                         72       60°                                                                              50                                                         120      25°                                                                              50                                                         120      60.sup.   35                                                         240      25°                                                                              40                                                         240      60°                                                                              40                                         2      1:1.9    24       60°                                                                              47                                                         72       25°                                                                              49                                                         72       60°                                                                              50                                                         120      25°                                                                              53                                                         120      60°                                                                              45                                                         240      25°                                                                              48                                                         240      60°                                                                              45                                         3      1:0.9    24       60°                                                                              >600                                                       72       25°                                                                              >600                                                       72       60°                                                                              >600                                       4      1:2.8    24       60°                                                                              >600                                                       72       25°                                                                              50                                                         72       60°                                                                              >600                                       5      1:4.0    8        60°                                                                              >600                                                       24       60°                                                                              >600                                       ______________________________________                                    

The heat aging tests in the above table show that a catalyst compositionhaving a platinum to chloride ratio of less than 1 and 4 or more gramatoms of chloride per gram atom of platinum does not maintain its levelofactivity over a long period of time.

What is claimed is:
 1. A process for the addition of an organosiliconcompound containing silicon-bonded hydrogen to an organic compoundhaving carbon-carbon unsaturation which comprises mixing anorganosilicon compound having silicon-bonded hydrogen with an organiccompound having carbon-carbon unsaturation in the presence of aplatinum-olefinic hydrocarbon complex containing more than one but lessthan 4 gram atoms of halogen per gram atom of platinum, saidplatinum-olefinic hydrocarbon complex is obtained from the reaction of aplatinum halide and an olefinic hydrocarbon selected from the groupconsisting of styrene and ring substituted styrenes in the presence of abasic material.
 2. The process of claim 1, wherein the organosiliconcompound containing silicon-bonded hydrogen is represented by theformula ##STR2## where R is selected from the group consisting of alkyl,cycloalkyl, aryl, alkaryl, aralkyl, haloalkyl and haloaryl radicals, Xis a hydrolyzable radical, c is a number of from 0 to 3, d is a numberof from 1 to 3 and the sum of c and d is from 1 to
 4. 3. The process ofclaim 1, wherein the organosilicon compound containing silicon-bondedhydrogen is an organopolysiloxane represented by the formula

    R.sub.y SiH.sub.z O.sub.4-y-z,

where R is selected from the group consisting of alkyl, cycloalkyl,aryl, alkaryl, aralkyl, haloalkyl and haloaryl radicals, X is ahydrolyzable radical, y is a number of from 0.5 to 2.49, z is a numberof from 0.001 to 1 and the sum of y and z is a number of from 1 to 2.5.4. The process of claim 1, wherein from 0.5 to 20 silicon-bondedhydrogen groups are present for each unsaturated carbon-carbon doublebond.
 5. The process of claim 1, wherein the mixture containing theorganosilicon compound having silicon-bonded hydrogen and the organiccompound having carbon-carbon unsaturation and platinum-olefinichydrocarbon complex is reacted at a temperature of from 10° to 200° C.6. The process of claim 1, wherein the platinum-olefinic hydrocarboncomplex is present in an amount of from 0.5 to 500 ppm by weight ofelemental platinum based on the weight of the mixture.
 7. The process ofclaim 1, wherein the platinum-olefinic hydrocarbon complex is preparedin the presence of an alcohol having from 1 to 6 carbon atoms.
 8. Theprocess of claim 1, wherein the platinum-olefinic hydrocarbon complex isreacted at a temperature up to 150° C. in the presence of a basicmaterial.
 9. The process of claim 1, wherein the basic material isselected from the group consisting of alkali metal carbonates and alkalimetal bicarbonates.
 10. The process of claim 1, wherein theplatinum-olefinic hydrocarbon complex is a platinum-styrene complex.